A Virtual Package is a technique of constructing a virtual package by dynamically combining a digital stream recorded on a read-only recording medium such as a BD-ROM and a digital stream recorded on a rewritable recording medium such as a hard disk, in order to develop the contents of the read-only recording medium. Suppose the digital stream recorded on the BD-ROM constitutes a movie work and the digital stream recorded on the hard disk constitutes a sequel to the movie work. This being the case, by constructing the above Virtual Package, the movie work recorded on the BD-ROM and the sequel recorded on the hard disk can be treated as one long feature film and submitted for playback.
For example, the following patent document describes a conventional technique about Virtual Packages.    Patent Document 1: Japanese Patent Application Publication No. 2002-369154